1. Field of the Invention
The present invention relates to a bearing mechanism for holding a shaft, a conveying apparatus in which such a bearing mechanism is applied to a conveying portion, and a recording apparatus in which such a conveying apparatus is used to convey a recording medium and an image is formed on the recording medium by a recording head.
2. Related Background Art
Recording apparatuses having a function as a printer, a copying machine or a facsimile, or recording apparatuses used as output devices for composite electronic equipments including a computer or a word processor or as output devices for work stations are designed that an image is on a sheet to be recorded (recording medium) such as a paper sheet or a plastic thin sheet based on image information.
Such recording apparatuses can be divided into an ink jet system, a wire dot system, a thermal system, a laser beam system and the like, in dependence upon a recording style.
In a serial type recording apparatus having a serial scanning system in which main scanning is effected along a direction transverse to a conveying direction (sub-scanning direction) of the sheet to be recorded, the entire image is recorded by recording means mounted on a carriage movable along the sheet to be recorded, by repeating one-line recording effected by the main scanning and a predetermined amount sheet feeding (pitch conveyance) alternately.
Among the above-mentioned recording apparatuses, the recording apparatus of ink jet type (ink jet recording apparatus) is designed to effecting the recording by discharging ink from recording means (a recording head) onto the sheet to be recorded. This recording apparatus has advantages that the recording means can easily be made compact, a fine image can be recorded at a high speed, the recording can be effected on a plain paper without special treatment, a running cost is inexpensive, noise can be suppressed due to non-impact recording and a color image can easily be recorded by using multi color inks.
Now, conveying means of a recording apparatus according to an earlier technology will be described with reference to FIGS. 13 to 18. FIG. 13 is a front view of such a recording apparatus and FIG. 14 is a sectional view of the recording apparatus.
A sheet feeding portion 503 is attached to a chassis 508 formed by bending a metal sheet. The sheet feeding portion 503 includes a conveying roller 536 for conveying a sheet Pxe2x80x2 and a PE sensor (sheet end detecting device) 532.
The conveying roller 536 is constituted by wounding an elastic material such as rubber around a surface of a metal shaft and is attached to the chassis 508 by mounting both ends of the metal shaft within conductive bearings 538, 539. A conveying roller tension spring 681 is disposed between the bearing 538 and the conveying roller 536 to apply load to the conveying roller 536 on rotating thereby to provide stable conveyance. Namely, by biasing the conveying roller 536 through the spring 681, predetermined load is applied.
The conveying roller 536 is attached as follows. First of all, one end of the metal shaft of the conveying roller 536 is inserted into the bearing 539 and then is attached to the chassis 508. Then, the other end of the metal shaft of the conveying roller 536 is passed through a cut out portion of the chassis 508. Then, the conveying roller tension spring 681 is attached and the bearing 538 is fitted into the chassis 508 while inserting the bearing 538 onto the shaft of the conveying roller 536 from outside. In this case, a pawl portion 686 of the bearing 538 enters into a groove portion 661 formed in the conveying roller 536, so that the conveying roller 536 is secured to the chassis 508. An assembled condition is shown in FIG. 15B.
A plurality of driven pinch rollers 537 abut against the conveying roller 536. The pinch rollers 537 are held by a pinch roller guide 530 pivotally mounted on a shaft 530a and are biased by a pinch roller spring 531 to urge the pinch rollers 537 against the conveying roller 536, thereby providing a conveying force for the sheet Pxe2x80x2.
The pinch rollers 537 are arranged so that they do not cover the entire area of the sheet Pxe2x80x2 but divided to hold only predetermined ranges of the sheet. In this case, the rotation shaft 530a of the pinch roller guide 530 is attached to bearings of an upper guide 533 for rotation.
Further, an inlet of the sheet feeding portion 503 to which the sheet Pxe2x80x2 is conveyed is provided with the upper guide 533 and a platen 534 which guide the sheet Pxe2x80x2. The upper guide 533 is provided with a PE sensor lever 535 for transmitting detection of leading and trailing ends of the sheet Pxe2x80x2 to the PE sensor 532.
The platen 534 is positioned by a bearing portion 642 fitted and slidable on the conveying roller 536 to be attached to the chassis 508, and an attachment shaft 643 directly attached to the chassis 508. Further, a sheet holding-down portion 544 for conveying a side edge of the sheet Pxe2x80x2 is provided at a sheet reference side of the platen 534.
With this arrangement, even if the side edge of the sheet Pxe2x80x2 is deformed or curled, the side edge of the sheet is prevented from floating to interfere with a carriage 550 or the recording head 507.
The recording head 507 for forming an image based on image information is disposed at a downstream side of the conveying roller 536 in a conveying direction of the sheet Pxe2x80x2.
In the above-mentioned arrangement, the sheet Pxe2x80x2 fed to the sheet feeding portion 503 is guided by the platen 534, pinch roller guide 530 and upper guide 533 to be sent to a pair of rollers (conveying roller 536 and pinch rollers 537).
In this case, the PE sensor lever 535 detects the leading end of the sheet Pxe2x80x2 being conveyed, thereby determining a printing position of the sheet Pxe2x80x2. Further, the sheet Pxe2x80x2 is conveyed on the platen 534 by rotating the pair of rollers 536, 537 by an LF motor (not shown).
Incidentally, the recording head 507 is an easy exchangeable ink jet recording head integrally formed with an ink tank. In this recording head 507, heat can be applied to ink by a heater or the like.
The ink is film-boiled by the heat to cause growth and contraction of a bubble to generate a change in pressure by which the ink is discharged from a nozzle 570 of the recording head 507, thereby forming the image on the sheet Pxe2x80x2.
In a sheet discharging portion 504, a transmitting roller 540 abuts against the conveying roller 536 and further abuts against a sheet discharging roller 541. Accordingly, a driving force of the conveying roller 536 is transmitted to the sheet discharging roller 541 through the transmitting roller 540. Further, a spur roller 542 abuts against the sheet discharging roller 541 to be driven by rotation of the sheet discharging roller 541.
The spur roller 542 is attached to a spur stay 641 of integral type provided on the platen 534.
By providing the spur stay 641 integral with the platen 534 in this way, since dimensions of the spur roller 542 and the sheet discharging roller 541 can be controlled within the same part, a dimensional relationship can be kept stably.
Further, the spur stay 641 has a partially cut-away portion 641a. When the head 507 is exchanged, the carriage 550 is moved up to the cut-away portion 641a to create a space through which a hook lever 553 for mounting and dismounting the head 507 can be manipulated.
With the above-mentioned arrangement, the sheet Pxe2x80x2 on which the image was formed in a carriage portion 505 is pinched by a nip between the sheet discharging roller 541 and the spur roller 542 to be conveyed and discharged onto a sheet discharging tray (not shown).
However, the above-mentioned technique has the following problems.
In the attachment of the conveying roller 536 to the chassis 508, as shown in FIGS. 5A and 15B, the groove portion 661 must be formed in the metal shaft of the conveying roller 536 and the pawl portion 686 must be provided on the bearing 538 corresponding to the groove 661 (FIG. 15A). Thus, the number of manufacturing steps is increased, thereby making the manufacturing cost more expensive. In addition, when the pawl 686 is disengaged, the pawl may be damaged, thereby causing a problem regarding operability.
Further, since the pinch rollers 537 do not hold down the entire area of the sheet Pxe2x80x2, as shown in FIG. 16, if the side edge of the sheet Pxe2x80x2 is warped, the sheet cannot enter below the sheet holding-down portion 644 but rides over the sheet holding-down portion 644, with the result that the side edge of the sheet Pxe2x80x2 may interfere with the carriage 550 or the recording head 507.
Furthermore, depending upon the kind of the sheet Pxe2x80x2 or surrounding environment such as temperature and humidity, a trailing end of the sheet Pxe2x80x2 may be floating after it was discharged. In such a case, if the trailing end of the sheet Pxe2x80x2 is pinched between the spur roller 542 and a spur roller cleaner 543 or a spur roller attaching portion 641 of the platen 534, poor sheet discharging will occur or the sheet Pxe2x80x2 will be damaged by the spur roller 542 (FIG. 17).
The present invention aims to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a bearing mechanism in which a groove portion in a shaft and a pawl portion on a bearing corresponding to the groove portion are not required and which can improve production efficiency and operability, and a conveying apparatus which has such a bearing mechanism and in which, when a driven roller is not located at an entire area of a sheet to be conveyed, a side edge of the sheet to be conveyed can be directed correctly not to damage the sheet to be conveyed after the sheet was discharged, and a recording apparatus having such a conveying apparatus.
To achieve the above object, the present invention provides a bearing mechanism comprising a supporting plate having an aperture portion for holding a bearing, and the bearing including a fitting portion to be fitted into the aperture portion of the supporting plate and having a shaft bore into which a shaft is to be inserted and two pinching portions protruded outwardly and axially spaced apart from each other by a distance corresponding to a thickness of the supporting plate at the fitting portion, and wherein the supporting plate is provided, around the aperture portion thereof, with cut-away portions through which the pinching portions can pass, and the pinching portions has fixing means for fixing the rotation of the bearing at a rotated position where the supporting plate is pinched by the pinching portions from inside and outside, by pinching the supporting plate from inside and outside by moving the pinching portions from the cut-away portions by rotating the bearing after the fitting portion of the bearing was fitted into the aperture portion of the supporting plate.
The fixing means may comprise a protrusion provided one of the pinching portion of the bearing and the supporting plate, and depression or hole portion provided in the other of the pinching portion of the bearing and the supporting plate.
One of the two outwardly protruded pinching portions may have a configuration greater than a configuration of the opposed other pinching portion, and an opening greater than the configuration of the other pinching portion may be provided at the opposed position.
The bearing may have a handle portion.
Further, in a conveying apparatus having a conveying roller and bearing mechanisms disposed at both sides of the conveying roller, at least one of the bearing mechanisms may comprise the above-mentioned bearing mechanism.
Further, in a conveying apparatus having a conveying means comprising a conveying roller and a driven roller opposed to the conveying roller with the interposition of a conveying path and divided into a plurality of roller portions along an axial direction, a guide member for holding-down a side edge of a sheet to be conveyed may be disposed at a position where the driven roller is not located and the side edge of the sheet to be conveyed is passed.
The conveying means may have a driven roller holding portion for holding the driven roller and the guide member may be provided on the driven roller holding portion.
The guide member may have a radius same as that of the driven roller in a sectional configuration at a nip portion between the conveying roller and the driven roller and may have a tapered configuration smoothly spaced apart from the conveying path, from the nip portion toward an upstream side of the conveying path.
Further, in a conveying apparatus having a sheet discharging roller and a spur roller opposed to the sheet discharging roller with the interposition of a conveying path, protection member for preventing a sheet from being caught up may be disposed between the conveying path and the spur roller at a downstream side of the conveying path.
The protection members may be provided on a spur roller attaching portion and may be disposed at least outside of both outermost spurs of the spurs.
Further, in a recording apparatus having a recording head for forming an image on a recording medium as a sheet to be conveyed, a carriage for holding the recording head and capable of scanning in a main scanning direction, guide means for guiding the carriage in the main scanning of the carriage, and conveying means for conveying the recording medium in a sub-scanning direction, the above-mentioned conveying apparatus may be provided.
Further, in a recording apparatus having a recording head for forming an image on a recording medium as a sheet to be conveyed, a carriage for holding the recording head and capable of scanning in a main scanning direction, guide means for guiding the carriage in the main scanning of the carriage, and conveying means for conveying the recording medium in a sub-scanning direction, the conveying means may comprise a conveying roller, a driven roller opposed to the conveying roller and divided into a plurality of roller portions along an axial direction, a platen for defining a guide surface during recording, and a holding-down member provided on the platen and adapted to prevent a side edge of a recording medium from floating, and a guide member for holding-down the side edge of the recording medium may be disposed at a position where the driven roller is not located and the side edge of the sheet to be conveyed is passed, and the guide member may comprise the holding-down member.